Re: too big min_free_kbytes
From: Shaohua Li <hidden>
Date: 2011-02-23 05:29:17
On Tue, 2011-02-22 at 22:25 +0800, Mel Gorman wrote:
On Mon, Feb 14, 2011 at 10:25:24AM +0800, Shaohua Li wrote:quoted
On Thu, Feb 03, 2011 at 10:58:08AM +0800, Andrea Arcangeli wrote:quoted
On Thu, Jan 27, 2011 at 04:27:55PM +0100, Andrea Arcangeli wrote:quoted
totally untested... I will test....The below patch is fixing my problem and working fine for me... as expected it can't possibly lead to any D state, it's pretty much like setting min_free_kbytes lower, and it's not going to alter anything other than the levels of free memory kept by kswapd. $ while :; do ps xa|grep [k]swapd; sleep 1; done 452 ? R 1:20 [kswapd0] 452 ? S 1:20 [kswapd0] 452 ? S 1:20 [kswapd0] 452 ? S 1:20 [kswapd0] 452 ? S 1:20 [kswapd0] 452 ? R 1:20 [kswapd0] 452 ? R 1:20 [kswapd0] 452 ? R 1:20 [kswapd0] 452 ? R 1:20 [kswapd0] 452 ? S 1:20 [kswapd0] 452 ? R 1:20 [kswapd0] $ vmstat 1 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 2 1 1784 111040 2393336 807924 0 0 63 992 56 70 1 1 96 2 0 1 1784 108928 2402556 801864 0 0 122624 0 1619 2150 0 5 80 16 0 1 1784 110664 2401244 801140 0 0 122496 0 1602 2081 0 3 81 16 0 1 1784 109796 2410184 792984 0 0 122752 0 1685 2149 0 4 80 16 0 1 1784 110416 2411856 791208 0 0 120448 4 1599 2075 0 4 81 16 1 0 1784 113516 2415344 785336 0 0 122496 0 1636 2125 0 4 81 15 I doubt we'll get any regression because of the below (see also my prev email in this thread), and I would only expect more cache and maybe better lru. Previously the free memory levels were stuck at ~700M now they're stuck at the right level for a 4G system with THP on (I'd still like to try to reduce the requirements only 1 hugepage for each migratetype in the set_min_free_kbytes to reduce the requirements to the minium, but only if possible..). But this saves 600M over 4G so it's the highest prio to address.Sorry for the later response, I offlined several weeks. The patch is addressing the 8*high_wmark issue, which isn't the original issue I reported (sure the 8*wmark issue should be fixed too). min_free_kbytes is set higher and cause more pages freed even no the 8*wmark issue. wmark: before: min 1424 after: min 11178The higher min_free_kbytes is expected as a result of using transparent hugepages so I don't really consider it a bug. Free memory going up to about 700M as a result of kswapd is a real bug though.quoted
in our test, there is about 50M memory free (originally just about 5M, which will cause more swap. Should we also reduce the min_free_kbytes?Either that or boot with transparent hugepages disabled and min_free_kbytes will be lower.
Fixing it will let more people enable THP by default. but anyway we will disable it now if the issue can't be fixed. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>